1. Field of the Invention
The present invention relates to millimeter waveguide shorts and methods for making such shorts and, more particularly, to a millimeter waveguide short comprising a metallic substrate, and alternate quarter-wavelength raised sections along a portion of the length of the substrate comprising a first layer of electrically conductive material deposited on the exposed major sides of the substrate and a second layer of an insulating material deposited on the outer surface of the first layer.
2. Description of the Prior Art
Waveguide shorts are used for various functions such as to tune various waveguide circuits. Such shorts have taken various forms, one of which was disclosed in U.S. Pat. No. 2,829,352 issued to S. R. Hennies et al on Apr. 1, 1958. The Hennies et al tunable waveguide short comprises a rectangular piston, a bearing member on each side of the piston for engaging the waveguide walls and a coil spring which engages the opposing waveguide walls.
Another waveguide short structure was disclosed in U.S. Pat. No. 3,049,684 issued to F. E. Vaccaro et al on Aug. 14, 1962 which comprises a choke mounted on the front end of a plunger which has slots for engaging cams on the waveguide walls to permit the short to be axially slideable in the waveguide. Still another short was disclosed in the article entitled "Sliding Short Eases Measurements" in Microwaves, Vol. 9, No. 12, December, 1970 at page 26 which comprises three cylindrical brass slugs separated by teflon slugs extending forward from a teflon block which is mounted forward of a block of lossy material.
The problem remaining in the prior art is to provide a waveguide short useable with millimeter waveguides which can be manufactured with more accurately controlled dimensional tolerances compared to the conventional machined structures found in the prior art.